1. Field of the Invention
The present invention relates to manipulator systems, and more particularly to computer controlled manipulators for performing assembly work.
2. Description of the Prior Art
In recent years, there have been proposed industrial manipulators equipped with tactile sensors to determine the position of the workpiece. In using a manipulator system to perform assembly work, generally, a large variety of assembly processes are involved. Therefore, a simple, yet flexible method to determine parts position and orientation by the manipulator system is required. Visual systems have been proposed. However, the industrial manipulator system may be located in a very hazardous environment, such as in smoke, steam, and dust. It also may be possible that many of the components to be assembled by the manipulator system may be of such a shape tht a visual system will not detect the profile of the object. Also, a visual system is limited to line of sight detection of an object.
In an article "Tactile Perception for Robot Devices," by M. H. E. Larcombe, in the First Conference on Industrial Robot Technology, University of Nottingham, U.S., Mar. 27-29th, 1973, pp.R16-191-195, a robot using tactile perception is described. On a movable robot on wheels is mounted a pincer style manipulator, which is covered by a tactile sensing surface. The requirement for a finger-like probe is suggested which would be articulated to allow feature tracing and some form of cylindrical or ellipsoidal sensing surface which may be rolled over features.
One problem associated with proposed manipulator devices is that the manipulator hand or fingers cannot be finely controlled in their movements near the workpiece just prior to making contact with the workpiece, often resulting in unintentional knocking over or displacement of the workpiece. One possible approach is to use the known proximity sensors available generally for detecting the presence of an object in their proximity. Here, however, the sensitivity of such sensors would require the manipulator to be very close to the objects for sensing and might not prevent the manipulator from bumping into objects. Also, if such proximity sensors were used with the fingers, they might physically interfere with the finger operation.